The concept of cooling a refrigerant flowing from a heat rejection heat exchanger to an expansion device in order to increase the capacity of the refrigerant system is well known. Such a refrigerant temperature reduction is most commonly accomplished in one of two ways, either by the inclusion of an economizer cycle or the use of a “liquid-suction” heat exchanger. However, each of these approaches has disadvantages. In the case of the economizer cycle, because of the need for additional components and extra complexity associated with a compressor, that has to be designed to accept vapor injection, a substantial expense is necessarily involved.
In the case of using a “liquid-suction” heat exchanger, the benefit is often limited, and under some circumstances, can actually reduce the cooling capacity of the refrigerant system. This occurs as the vapor entering the compressor is additionally superheated in the “liquid-suction” heat exchanger, which reduces the density of the refrigerant entering the compressor, and thus the refrigerant mass flow available for cooling. Therefore, the additional preheating of refrigerant as it enters the compressor often negates the effect of additional cooling provided by a “liquid-suction” heat exchanger.
There is therefore a need for increasing capacity of a refrigerant system in a simple, effective and less expensive manner.